The locus of the antimitotic drug effect on steroidogenesis in Y-1 adrenal tumor cells lies beyond cAMP generation but may be on the kinase or later steps. We have also shown that adenylate cyclase may be associated with microtubules in brain preparations whereas little Ns protein and no receptor is purified along with the microtubule protein. A direct association between such a location of adenylate cyclase and the effects of antimitotic drugs has not yet been possible.